Fiber-bonded electrodes



y 1962 L. F. URRY FIBER-BONDED ELECTRODES 2 Sheets-Sheet 1 Filed Nov. 3, 1959 May 8, 1962 Filed Nov. 3, 1959 Felted non-woven fabric L. F. URRY 3,033,909

FIBER-BONDED ELECTRODES 2 Sheets-Sheet 2 Powdered Active Fibrous side down Maierlai Pl Metallic ectrode @du Current Collecfor May be cut Vibrator i0 Sehle Mix to shape Hear and Pressure Roll of Pile Fabric i 01.4 g 1.3 LLI 312 g 11 1.0

o 1 2 a 4 HOURS O 1.3 o '1.2 g

1.1 5 1.0 I 5 4+hCYCLE o .9 CYCLE HOURS INVENTOR. L E WI 3 F. U R RY BY A TTORNEV Unite States This invention relates to fiber-bonded electrodes for use in heavy duty primary and secondary cells wherein said fibers are used in the form of a pile.

It has already been suggested to use fibers of a suitable thermoplastic material as the bonding agent for strong,

flexible, high-capacity electrodes. In this practice the dry electrode containing a small amount (1 to 7 weight percent) of the fibers is'presscd onto asuitable metallic current collector and simultaneously heated to the softening point of the plastic fibers. The fibers are thereby self-welded to each other, forming an interlocking network of fibers which serves to hold the mix particles together.

Certain modifications of the above-identified method are desirable for large scale commercial manufacture of the electrodes. A particular problem to be overcome is that of separation of the fibers from the dry electrode mix prior to fabrication of the electrodes. Since the plastic fibers are fluffy and much lighter in weight than the remainder of the material in the mix, settling of the heavier mix particles tends to occur, particularly in large batches. Thus, the proportion of bonding fibers to active. particles in the mix may not remain constant in a series of electrodes made therefrom.

With the above in mind, the major object of the present invention is to provide novel fiber-bonded electrodes having a continuous supply of the required amount of fibers.

A related object of the invention is. to provide electrodes having a strong network of interlocking bonding fibers steadfastly supporting and. retaaining the active paratent O ticles therein, even when the electrode is subjected to ex cessive handling or shock.

In the drawing:

PEG. 1 is a side elevational view of an electrode structure for the electrodes of the invention;

FIG. 2 is a side elevational view of the subject electrodeshowing the disposition of its collector grid screen;

FIGS. 3 and 4 are fragmentary cross-sectional views of the instant electrode at difierent stages of fabrication;

FIG. 5 is a schematic representationof a typical assembly line based on the method of the invention; and

FIGS. 6 and 7 are graphs showing respectively the performance of Leclanch and nickel-cadmium cell systems using the subject electrodes. I

As shown on FIGS. 1 through 4 inclusive, the electrode of the invention comprises a sheet of woven or non-Woven thermoplastic material which may consist of fibers of vinyl choloride-vinyl acetate attachedto a backing sheet of a felted non-woven fabric made of vinyl chloride-vinyl acetate and regenerated cellulose.

In the felted backing sheet, the vinyl chloride-vinyl 21Cfi,

ice

pile fabric. Vibration may be needed to permit the current collector 12 to settle down over the upright fibers as illustrated in FIG. 2. An electrostatic charge may be employed to hold the fibers upright. The dry powdered mix of electrochemically active materials is then sifted onto the projecting fibers and settled in place between the fibers by some method such as vibration. The fibers then continue to project above the collector grid and powdered mix as shown in FIG. 3. The tops oi'the-fibers' are left clean and exposed in order to make a complete weld to the fibers in the sealing sheet. The final step then consists of placing a woven or non-woven'felted sheet 14 containing thermoplastic fibers, such as Viskon-Vinyon, on top ofthe protruding fibers 10. and applyingsufiicient pressure (upto 5 tons per square inch) and heat to bond the fibers to side a of the sheet 14. [Viskon-Vinyon is a trade name for a felted non-woven fabric containing Vinyon (vinyl chloride-vinyl acetate)? fibers and Viskon (regenerated cellulose.) fibers.] The fibers thus bonded on both ends to sheets 8 and 14 form a strong network supporting and retaining the. active particles even when the electrode'is hand-led excessively. A minimum of spaceis: needed for the fibers to achieve maximum bonding. This completed structure, which is illustrated in FIG. 4, may be compared to a stitched.sandwic without the space loss and cover sheet perforations accompanying any mechanical stitching operation. FIG. 5, illustrates a typical assembly line set up based on the-subject method, Rolls of the selected thermoplastic pile fabric and the metallic current collector'mat eri-almay be automatically unr'oll'ed' and assembledtogether. The powdered active material may then be fed from a hopper onto the moving, iabric. at a rate sufiicient to provide the desired amount of active material per unit area. Finally, the top plastic sheet is brought into contact with and heat-sealed to the fibers in. the pile fabric as previously described. The finished electrode may then be cut into the desired shape and assembled into a cell.

Electrodes for various acid and alkaline electrolyte systems may be constructed by the subject method. The main requirements for selecting the fibrous material are that the fibers and sheets be thermoplastic and stable in the cell-environment. The pile backing may be constructed of various Woven and non-woven materials other than the .Viskon-Vinyon described earlier, provided that the material is adaptable to pile fabrication techniques, such as adhesion orstitching. Felted Dynel is suitable for use in acid or alkaline systems and woven nylon may be used indilute alkaline environments.

As an example of the subject invention, the following formulation may be employed in the manner described above to construct MnO cathodes which are suitable for use either in acid or alkaline cell environments:

Formula 1 Percent by weight. Manganese dioxide -a Graphite powder 20 The following is an example of a'nicltel oxide cathode I and durable, high rate cathode for nickel-cadmium cells:

Formula 2 Percent by weight Nickel hydroxide powder 77.6 Graphite I 22.4

Formula 3 Percent by weight Powdered cadmium 43.40 CdO V 46.55 Carboxymethylcellulose (CMC) 1.45 Fe() 8.60

Twelve grams "of the above were suflicient for a 2.9

inch by 3.6 inch by 0.03 inch electrode. The CMC may be omitted from the above formula, if desired, and finely formulation which was used to construct an inexpensive 4 (FormulasZ and 3) were bonded by means of the subject method. 7

The cell, the performance of which is illustrated on FIG. 6, consisted of two positive plates having the dimensions 10 sq. in. by 0.03, and contained 8.5 grams of mix per plate. The capacity of the plates which had a total of 17 grams of mix was found to be 3.35 ampere hours. The collector for the plates was a metal grid coated with a conductive carbon paint. The negative electrodes were 7 made of sheet zinc.- The cell Was discharged under a 4 ohm continuous discharge with the indicated result- In the case of FIG. 7, the cell consisted of two positive and three negative in. 2 by 0.03 inch plates. Again, a

powdered nickel may be substituted for the iron oxide.

Other metal anodes, e.g., zinc, may also be constructed according to the subject invention. A suitable Zinc anode formulation for use in alkaline cells is the following:

Formula 4 V Percentbyweight Zinc powder, 4% amalgamated CMC and 'HgO may be omitted, so that only the pow-,

dered zinc is employed. a

FIGS. 6 and 7, respectively, show the excellent discharge characteristics'of a fiber-bonded MnO 'cathode (Formula 1) in a Leclanch primary cell and of a rechargeable nickel-cadmium cell wherein both electrodes 4 ohm continuous discharge was employed. The similarity between the first and fourth discharge cycles should be noted. 7 i

What is claimed is: v

1. An electrode comprising a "felted non-woven fabric encasing a metal collector having perforations therein, thermoplastic fibers protruding through said perforations, electrochemically active particles supported and retained by said fibers, the protruding ends of said fibers being heat-sealed to said fabric.

2. ,The electrode of claim 1 wherein said electrochemically active particles consist of, nickel hydroxid and graphite.

3. The electrode of claim 1 wherein said electrochemically active particles consist of manganese dioxide and graphite. V 1

4. The electrode of claim 1 wherein said electrochemically active particles comprise cadmium, cadmium oxide. and iron oxide. Y

5. The electrode of claim 1 wherein said electrochemically active particles comprise zinc, zinc oxide and mercuric oxide.

il ief erences Cited in the file of this patent UNITED STATES PATENTS 651,471 Ribbe" June 12, 1900 682,899 DArnoult Sept. 17,,1901 2,247,091 'luman June 24, 1941 2,610,220 Brennan Sept. 9, 1952 2,616,938 Brandt Nov. 4,1952 FOREIGN PATENTS 467,696 Great Britain June 22, 1931 

1. AN ELECTRODE COMPRSING A FELTED NON-WOVEN FABRIC ENCASING A METAL COLLECTOR HAVING PERFORATIONS THEREIN, THERMOPLASTIC FIBERS PROTRUDING THROUGH SAID PERFORATIONS, ELECTROCHEMICALLY ACTIVE PARTICLES SUPPORTED AND RETAINED BY SAID FIBERS, THE PROTRUDING ENDS OF SAID FIBERS BEING HEAT-SEALED TO SAID FABRIC. 